The broad objectives of the progran are to conceive, explore and translate into practive the use of radioactive tracers in medical diagnosis and health-related research. Although our overall objectives have remained unchanged as this field, which has come to be widely known as nuclear medicine, has grown, specific areas of emphasis for development of new applications have evolved with the availability of new tracers, new techniques, etc. At present our goals for developing new applications of radioactive tracer techniques are directed toward seven specific areas, as follows: (1) invention and development of radiometric chemical assays based on the use of non-immune binders of the substances being measured; (2) extension of radiometric assay techniques to the in vitro study of other micro-organisms of clinical importance, such as M. tuberculosis, M. leprae, and viruses; (3) evaluation of the application of radiometric assays to the study of factors influencing cellular metabolism, beginning with human lymphocytes and polymorphonuclear leukocytes; (4) new methods of labeling compounds for in vivo and in vitro nuclear medicine applications; (5) functional imaging of various body organs including the brain, heart, peripheral circulation, liver and kidney, using an Image Display and Analysis (IDA) system developed as part of this program; (6) application of radioactive tracers in non-invasive studies of the heart; and (7) tracer studies of peripheral vascular disease.